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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.c++,comp.lang.ada
Subject: Re: Why use C++?
Date: Fri, 12 Aug 2011 23:22:05 +0200
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Date: 2011-08-12T23:22:05+02:00
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Jed writes:
>> When have you last thought about the size of the components
>> of std::string, of of a vtable?  Why, then, is there a
>> pressing need to think about the sizes of int types?
>
> You know that that was a very bad comparison. Completely invalid.

On the contrary I think this comparison is perfectly valid.  The
language should distinguish between integers (i.e. numbers) and various
kinds of machine registers.  If you think you need to know the number of
bits in an int, this indicates you are dealing with low-level stuff and
therefore need something much more precise than "int", which specifies
not only size in bits but also bit-endianness, byte-endianness,
alignment, permissible operations and, if arithmetic is possible at all,
overflow semantics.  C conveniently ignores all these things and leaves
them unspecified.  With Ada, the programmer can specify most of those
aspects (except, sadly, for byte-endianness).

If you confuse "size of an int" for "range of permissible values for an
int", then you ignore the possibility that the range might not fit at
all with any size in bits, e.g.

subtype Fridge_Temperature is range 250 .. 313; -- kelvins

Most of the time, you do *not* need to know the size of an int; instead
you need to know the size of a hardware register, field in a network
protocol, etc and these are, quite often, *not* numbers.

-- 
Ludovic Brenta.
The Chief Legal Officer proactively enables our potentials.